National Coral Reef Monitoring Program
Climate Monitoring Brief: Flower Garden Banks National Marine Sanctuary
Orbicella faveolata in St. Croix, USVI
Atlantic Oceanographic & Meteorological Laboratory Coral Program
University of Miami Cooperative Institute of Marine and Atmospheric
Science
National Oceanic Atmospheric Administration
N. Besemer, A. Palacio, A. Webb, I. Enochs - December 2022
Mission
The AOML Coral Program tracks the status and trends of coral reef ecosystems of the U.S. Atlantic and Caribbean as part of the National Coral Reef Monitoring Program (NCRMP). This summary brief provides an overview of the most recent climate monitoring efforts at Flower Garden Banks National Marine Sanctuary (FGBNMS).
Expedition summary
- The AOML Coral Program conducted NCRMP climate monitoring operations at FGBNMS from October 3rd to October 8th, 2022
- A total of eight different sites were visited by ten team members and sanctuary collaborators completing a total of 98 dives.
Data collection summary
Subsurface temperature Subsurface temperature recorders (STRs) were recovered and redeployed at east and west bank transects, each one composed by 4 depths (Fig. 1). In total, more than 4 million temperature observations were collected (Table 1)
| Transect | 21m | 25m | 30m | 35m | Total |
|---|---|---|---|---|---|
| East | 772,166 | 772,334 | 772,301 | 772,097 | 3,088,898 |
| West | NA | 399,148 | 446,378 | 529,033 | 1,374,559 |
NCRMP Climate Fixed Sentinel Site Monitoring
At our East Buoy 3, 15m site, located on the East Bank, short term instruments (72h) were deployed to monitor daily fluctuations in:
- Current: 284 observations
- pH: 285 observations
- Light: 288 observations
- Carbonate chemistry: 21 samples collected
Habitat persistence
Changes in Bioerosion and accretion were monitored
Carbonate budget surveys: Benthic cover, sponge, urchin and parrotfish surveys completed at 6 transects
Bioerosion: 14 Bioerosion Monitoring Units (BMUs) collected, 15 redeployed
Calcification: 5 Calcification Accretions Units (CAUs) collected, 5 redeployed
Benthic cover: 6 landscape mosaics
Figure 1: Study sites and depths in Flower Garden Banks
Subsurface Temperature
The temperatures that marine organisms experience are a function of depth and local oceanographic conditions. To monitor this, two cross-shelf transects were established at each bank within the sanctuary. Four years of temperature measurements were retrieved at the East bank (4 depths) and seven at the West bank (3 depths, Fig. 2). Temperature was measured using SeaBird Electronics Subsurface Temperature Recorders (STR)s that collected data at 5-minute intervals. The STRs from west bank were not able to be collected during the last field monitoring trip in 2019. We have included the entire temperature data collection from east bank for better comparison to west bank.MORE TO THIS.
Figure 2: Temperature conditions at two transects in FGBNMS (east bank, and west bank) representing a depth gradient (21m, 25m, 30 and 35m). Data were collected from September 2015 to October 2022. However, STR from west Bank - 15m was not recovered.
Temperature values were lower in the deeper stations (30 and 35m) of both east and west banks. A particular cold winter was recorded in the year 2021, when monthly mean temperatures were below 20.6\(^\circ\)C at all depths. September of 2016 was the hottest month recorded in both banks, with mean temperatures higher than 30.76\(^\circ\)C) at the 21, 25 and 30m stations, and higher than 29.77\(^\circ\)C) at the 35m stations (Fig. 2).
Diurnal Suite Deployment
Seawater carbonate chemistry can fluctuate diurnally, due to biological forcing and processes such as photosynthesis and respiration, as well as calcification and dissolution. To characterize this, a suite of instruments were deployed for a 72-hour period at the East Bank 15m site, East Buoy 3 (Fig. 3). A SeaFET was used to log pH, an EcoPAR measured Photosynthetically Active Radiation (PAR), and a Lowell Tiltmeter measured current speed and direction. Each collected measurements at 15-minute intervals.
To accompany and validate the diurnal suite, discrete water samples were collected at three-hour intervals (n=21) using Subsurface Automatic Samplers (SAS, https://www.coral.noaa.gov/accrete/sas/). These samples will be analyzed for Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC), and Spectrophotometric pH (SpecpH). Using these metrics, we can get the calculated values for pCO2 and aragonite saturation state which provide the full suite of carbonate chemistry parameters.
Figure 3: Data from East Buoy 3 diurnal suite monitoring from October 4th to Oct 7th. Top panel: pH and temperature from SeaFET. Bottom panel: Photosynthetically Available Radiation (PAR) and current speed from EcoPAR and Tiltmeter. Grey blocks denote night time throughout sequence of the plot. Instruments measured parameters every 15 minutes.
Figure 4: Submered Automated Samplers (SAS) deployed to collect water samples every 3 hours
Habitat persistence
Carbonate budget assessments use transect-based surveys to quantify the abundance of carbonate producers, such as corals and crustose coralline algae, as well as carbonate bioeroders, such as grazing parrotfish and sea urchins. Abundances are multiplied by taxon- specific rates of carboante alteration to determine if a reef is in a state of net accretion (habitat growth) or net loss (habitat loss). At East Buoy 3, six transects were established and surveyed in 2015 to obtain carbonate budgets. We revisited this site in 2019 and 2022 to find out the new status of carbonate budget after six years. The transect results showed that carbonate budgets have decreased in 2022. This trend is driven by a reduction in coral cover and calcification as well as a steep increase in parrotfish erosion. MORE SUMMAITON TEXT FOR FGB CARB BUDGETS
Figure 5: Carbonate budgets from East FGB in 2015, 2019 and 2022 and the processes contributing to calcification and bioerosion. The horizontal line in the “Net carbonate production panel” denotes accretionary stasis, the point where the budget flips from habitat grpwth to loss. PF represents parrotfish.
Landscape mosaics are used to quantify the benthic community, and to monitor changes in coral cover over time. Thousands of underwater images are digitally stitched together to create a high-resolution archive of the reef at the time of collection.
